Did you ever figure this out? I've stopped receiving them as well.
I didn't get a report over the weekend.I've just turned them back on, so we'll see what happens. I'm not on iOS 13.
And now that I said that - I got one this morning. Go figure.I haven’t gotten one in a couple of months or more.
If you do a hard reset or even turn your iPhone off for s period of time you will not get a ScreenTime Notification